1. Field of the Invention
The present invention generally relates to spinal fixation and fusion systems. An embodiment of the present invention relates to an insertion guide used during the insertion of a spinal implant into a disc space between a pair of vertebrae. The implant may be used for correction, fixation, and/or stabilization of a spinal column.
2. Description of the Related Art
An intervertebral disc that becomes degenerated may have to be partially or fully removed from a spinal column. Intervertebral discs may become degenerated due to various causes such as trauma, disease, or aging. Removal or partial removal of an intervertebral disc may destabilize the spinal column. A spinal implant may be inserted into a disc space created by the removal or partial removal of an intervertebral disc. The spinal implant may maintain the height of the spine and restore stability to the spine. Bone may grow from adjacent vertebrae into the spinal implant. The bone growth may fuse the adjacent vertebrae together.
A spinal implant may be inserted using an anterior, posterior or lateral spinal approach. An anterior spinal approach may require less bone removal and muscle distraction than a posterior spinal approach. Also, an anterior spinal approach may involve less risk of nerve damage than a posterior spinal approach. Intervertebral disc location or other factors may contraindicate an anterior spinal approach.
During an anterior spinal approach, a surgical opening may be made in the abdomen of a patient. The opening may be 25 centimeters (10 inches) or more in depth for some patients. The opening needs to be large enough and deep enough to accommodate instrumentation that inserts a spinal implant within a disc space. A discectomy may be performed to remove portions of a defective or damaged intervertebral disc and create the disc space. The amount of removed disc material may be determined by the size and type of implant that will replace the removed disc material.
The implants may be constructed of any biocompatible materials sufficiently strong to maintain spinal distraction including, but not limited to, bone, metals, ceramics and/or polymers. Implants may be packed with bone graft or a synthetic bone graft substitute to facilitate spinal fusion. Implants may have a variety of shapes, which include, but are not limited to, threaded cylinders, unthreaded cylinders, and parallelepipeds.
A protective sleeve may be used during preparation and insertion of a spinal implant. The protective sleeve may serve to protect abdominal organs, blood vessels and other tissue during a spinal implant procedure using an anterior approach. The sleeve typically extends above the surgical opening during use. The sleeve may maintain distraction of the vertebrae. Also, the sleeve may serve as an alignment guide for tool and implant insertion during the surgical procedure. Protective sleeves may also be used during a spinal fusion procedure using a posterior or lateral approach.
Protective sleeves typically have distractors on a distal end. Distractors are projections that may be inserted into a disc space during a spinal fusion procedure. The distractors may serve to achieve and maintain distraction of adjacent vertebrae. Distractors may also help to secure the protective sleeve to the vertebrae during the procedure. Protective sleeves may have one tube or two parallel tubes. FIG. 1 shows a single-tube protective sleeve, and FIG. 2 shows a dual-tube protective sleeve.
FIG. 1 illustrates a single-tube protective sleeve 30 that may be used in a spinal fusion procedure. A spinal fusion procedure may involve the insertion of one or more implants in a disc space between two vertebrae. Protective sleeve 30 may include a long, hollow tube 32; two distractors 34 on opposite sides of an end of the tube; and two spikes 36 (only one shown) on opposite sides of the end of the tube. Protective sleeve 30 is typically sufficiently long to allow access to a disc space of a large patient during an anterior procedure. Protective sleeve 30 may also be used in a posterior spinal fusion procedure.
A spinal fusion procedure may involve the insertion of two implants in an intervertebral disc space. A discectomy may be performed to provide space for an initial distractor. The initial distractor may be inserted into the disc space. The initial distractor may be rotated to establish an initial separation distance between a pair of vertebrae that are to be fused together. The initial separation distance may be large enough to allow a width of the protective sleeve distractors 34 to fit between the vertebrae. More disc material may be removed adjacent to the initial distractor to accommodate insertion of the protective sleeve distractors 34. A protective sleeve 30 may be placed over the initial distractor. A cap (not shown) may be placed on end 38 of the protective sleeve 30 opposite distractors 34 to protect the end of the sleeve during insertion. Distractors 34 may then be hammered into the disc space by striking the cap with a mallet (not shown). Spikes 36 may be hammered into vertebral bone to stabilize protective sleeve 30 during the implant insertion procedure. Distractors 34 may serve to separate the adjoining vertebrae to a desired separation distance. The cap and initial distractor may be removed from the protective sleeve
After insertion of a protective sleeve, a hole may be drilled in the intervertebral disc by inserting a tool with a reaming head attachment through tube 32 and rotating the tool until a predetermined depth is reached. The reaming tool may also remove portions of the end plates of the adjacent vertebrae. In some procedures, the hole is then tapped by inserting a tool with a tap head attachment into tube 32. The tapping tool may be rotated and driven downward until a predetermined depth is reached. After the hole is prepared, an implant may be inserted in the hole by attaching the implant to an implant insertion tool and inserting the implant into the disc space through tube 32. For untapped holes, the implant may be hammered into the hole by striking the implant insertion tool with a mallet. For tapped holes, the implant may be threaded into the hole by rotating the implant insertion tool. The implant insertion tool and the protective sleeve may be removed from the patient.
If a second implant is to be inserted, an initial distractor and cap may be utilized during insertion of the sleeve into the disc space adjacent to the first implant. A hole may be prepared and the second implant may be inserted into the disc space. Alternatively, the protective sleeve 30 may remain inserted in the disc space, and a second single-tube protective sleeve 30 may be inserted adjacent to the protective sleeve. A hole may be prepared and the second implant may be inserted into the disc space through the second sleeve.
The optimal alignment and spacing of implants in a spinal fusion procedure may be determined before surgery. Achieving the predetermined alignment and spacing during surgery may be important to achieve optimal fusing of the adjacent vertebrae. Protective sleeve 30 has characteristics that may make achieving alignment difficult. First, each of the two holes is aligned, reamed, and tapped in a separate procedure. It is often difficult to align and space the holes correctly. Second, the alignment of protective sleeve 30 must be maintained after insertion. Any slight movement of protective sleeve 30, which may act like a lever arm, may result in misalignment of the hole.
FIG. 2 illustrates a dual-tube protective sleeve 40 used in a spinal fusion procedure involving the insertion of two implants into a disc space between a pair of vertebrae. A dual-tube protective sleeve 40 may include long, hollow tubes 32; one or more distractors 34; and one or more spikes 36. Protective sleeve 40 is typically long enough to allow access to an intervertebral disc in a large patient during an anterior procedure. Spinal fusion using implants with protective sleeve 40 may involve the insertion of two implants in a parallel, bilateral position within a disc space.
A discectomy may be performed to provide space for initial distractors. A pair of initial distractors may be inserted into the disc space at desired locations. The initial distractors may be rotated to establish an initial separation distance between the vertebrae. The initial separation distance may allow end of distractor 34 to fit between the vertebrae. More disc material between the initial distractors may be removed to accommodate the distractor 34. A cap (not shown) may be placed on the end 42 of protective sleeve 40 opposite distractor 34. Distractor 34 may be hammered into the disc space by striking the cap with a mallet (not shown). Spikes 36 may be hammered into disc bone on the adjacent vertebrae to help stabilize protective sleeve 40 during the procedure. Distractor 34 may serve to separate the adjoining vertebrae to a desired separation distance.
After coupling the dual-tube protective sleeve to the vertebrae, holes are reamed in the disc space by inserting a tool with a reaming head attachment through tubes 32 and rotating the tool until a predetermined depth is reached. During formation of the holes, a portion of end plates of the vertebrae may be removed so that implants inserted into the holes will contact the vertebrae. In some procedures, the holes are tapped by inserting a tool with a tap head attachment through tubes 32 and rotating the tool until a predetermined depth is reached. After the holes are prepared, implants may be inserted in the holes by attaching the implants to an implant insertion tool and inserting the implants through tubes 32. For untapped holes, the implants may be hammered into the hole by striking the implant insertion tool with a mallet. For tapped holes, the implants may be threaded into the holes by rotating the implant insertion tool. The implant insertion tool is removed. Protective sleeve 40 is also removed.
FIG. 3 shows a representation of implants inserted into disc space 44 using a dual-tube protective sleeve 40. Spinal nerves in the spinal canal 46 are protected by dura 48. Nerves 50 extend from the spinal canal 46. Implants 52 are inserted between two vertebrae 54 (one shown). Care must be taken during insertion of the implants 52 to make sure that the implants do not impinge on the nerves 50.
Like single-tube protective sleeve 30, dual-tube protective sleeve 40 has characteristics that make it difficult to align the implants correctly. First, the alignment of protective sleeve 40 must be maintained after the protective sleeve is coupled to the vertebrae. Any slight movement of sleeve 40, which may act like a lever arm, may result in misalignment of the holes. Second, the long parallel tubes make it difficult to angulate the two implants 52 relative to each other. Angulated implants may be the desired alignment in some spinal fusion procedures. Using a dual-tube protective sleeve 40 has the advantage that the surgical procedure is simplified because there is only one insertion procedure, as opposed to two insertion procedures for a single-tube protective sleeve 30.
Single-and dual-tube protective sleeves share some disadvantages. First, the sleeves are typically unitary members that are long enough to extend out of a 25-centimeter (10 inch) deep surgical opening after being hammered into place. To maintain alignment after insertion, the sleeve must be kept as motionless as possible. The sleeve tends to act like a lever arm, and any slight motion of the sleeve during the procedure may result in misalignment of the implants. The sleeve acting as a lever arm is particularly problematic when the sleeve is handed off during the surgical procedure from one member of the surgical team to another member of the surgical team.
A second disadvantage of protective sleeves is related to the first disadvantage. The sleeve is held in place only by the distractors and the spikes inserted in the disc space. This connection may not be very secure. Because the connection is not secure, the sleeve may have to be held by the members of the surgical team throughout the entire procedure to maintain proper alignment. As noted above, any slight movement can result in the misalignment of the implants.
A third disadvantage of protective sleeves is that they may afford minimal protection to surrounding tissues during a spinal fusion procedure. Major blood vessels, parallel the anterior surface of the spine for much of the spine""s lower length. These vessels may be retracted during a spinal fusion procedure. The interface between the distal end of the sleeve and the spinal column is typically not a perfect fit. Gaps may exist between the sleeve and the vertebrae. The presence of gaps creates the risk of drill bits, taps, and implants coming into contact with the blood vessels or other tissue during the procedure. Also, the blood vessels may be pinched between the sleeve and the vertebrae. A nick or cut to a major blood vessel can be life threatening.
Removal of disc material (anulus fibrosus and nucleus pulposus) from the disc space may require special instrumentation. For example, disc material that may be pulled from a disc space with a long rongeur that extends through the sleeve. The length of the rongeur may require that the rongeur be a specially made instrument.
The above-mentioned methods and systems inadequately address the need to angulate implants in some spinal fusion procedures, the need to maintain precise alignment throughout the procedure, and the need to protect surrounding tissues during the procedure. It is therefore desirable that an improved method and system be derived for inserting spinal implants during a spinal fusion procedure.
A holder or base may allow instruments and spinal implants to be inserted into a disc space during a spinal fusion procedure. The holder may provide a base for a sleeve or sleeves during the spinal fusion procedure. When a sleeve is not being utilized during the procedure, the sleeve may be removed from the holder. The ability to remove the sleeve when the sleeve is not being utilized may prevent the sleeve from being unintentionally used as a lever arm to change the position of a first vertebra relative to a second vertebra during the spinal fusion procedure.
A holder may include a body, one or more sleeve conduits passing through the body from the top to the bottom, and one or more distractors on the bottom of the body. The holder may also include one or more tangs or fastener openings that allow the holder to be affixed to adjacent vertebrae. The body may have a smooth outer surface with no sharp corners or edges. A bottom surface of the holder may be shaped to conform to a shape of an exterior surface of the vertebrae. In some embodiments, the body may be flared near the bottom to provide shielding for surrounding tissue. The flared body may provide the holder with a stable base against vertebrae that are to be fused together.
Sides of a body of a holder may include openings or indentations. The openings or indentations may reduce the weight of the holder. The openings or indentations may also allow an insertion instrument to be easily and strongly coupled to the holder. For a dual sleeve holder, an embodiment of the insertion instrument may be narrow and/or include channels so that the insertion tool may be inserted over initial distractors without the initial distractors contacting the insertion tool. For a single sleeve holder, a sleeve and a cap for the top of the sleeve may be used as the insertion tool. Alternately, a separate insertion tool may be coupled to an opening or indentation of the single sleeve holder to insert the holder between the vertebrae. A separate insertion tool may be used if the sleeve includes a window that could allow the sleeve to bend or deform when the sleeve the holder is impacted into the disc space.
A flange may be placed around a portion of the body of a holder near vertebrae that are to be fused together. The flange may protect tissue and blood vessels from harm during a spinal fusion procedure. Major blood vessels, such as the aorta and the vena cava, may be placed on top of the flange to position the vessels in a known location where the vessels will not be pinched or nicked during the procedure. The flange may inhibit tissue from being pinched, nicked, or otherwise harmed during the spinal fusion procedure. The flange may be made of a rigid or semi-rigid material. A portion of the flange may be made of an elastic material so that the flange may stretch over and slide down the holder. In one embodiment, the holder may include a rim for holding the flange in place after installation. In another embodiment, the holder may include a groove for holding the flange in place. In another embodiment, the flange has an elastic collar, which holds the flange in place against the holder.
A sleeve may be placed within a sleeve conduit of a holder during a spinal fusion procedure. Instrumentation may be inserted through the sleeve to prepare the disc space for an implant. The instrumentation may include, but is not limited to drills, taps and tissue removers. The implant may be inserted into a prepared disc space through the sleeve. In some holder embodiments, an inner surface of a sleeve conduit may include a shoulder to limit the insertion distance of a sleeve into the conduit. Above a shoulder, a conduit may be sized to match the outer diameter of a protective sleeve. Below the shoulder, the conduit may be sized to match the outer diameter of instrument heads and implants to be used in the procedure. In some embodiments, the shoulder may include slots configured to engage distractors on protective sleeves. The slots may allow the holder to be used with single-tube protective sleeves that include distractors.
Embodiments of a holder may have non-circular conduits. The cross sectional shape of the holder conduits and the protective sleeves inserted into the holder may be any desired shape that allows for the insertion of spinal implants into a disc space. For example, the cross sectional shape of the conduits may be rectangular if the cross sectional shape of the spinal implants are generally rectangular. Other embodiments of the holder may have overlapping circular conduits or conduits which do not have a regular geometric shape. Embodiments of holders that have circular conduits may be constructed with conduits of different diameters to accommodate protective sleeves and implants of different diameters.
Embodiments of holders may be provided with non-parallel angled conduits. Non-parallel conduits allow the insertion of implants at oblique angles to improve spinal fusion and to protect nerves posterior to the disc space. Other holder embodiments may have parallel conduits.
In an embodiment of a holder, a distractor or distractors of the holder are driven into an intervertebral disc space. In an embodiment of a dual sleeve holder, the holder has a central distractor between sleeve conduits of the holder. In an embodiment of a dual sleeve holder, the holder includes a pair of lateral distractors located near opposite ends of the sleeve conduits. In an embodiment of a dual sleeve holder, the holder includes a central distractor, and a pair of lateral distractors located near opposite ends of the sleeve conduits. In an embodiment of a single sleeve holder, the holder may include a pair of distractors located near opposite ends of a sleeve conduit. A distractor of a holder may establish a separation distance between adjacent vertebrae. A distractor may secure the holder to the vertebrae.
Distractors may include a wedge-shaped portion to facilitate distraction of a pair of adjacent vertebrae. Distractors may include curved guide surfaces that guide an implant or instruments to desired positions within a disc space. A portion of an outer surface of a distractor may include serrations or surface roughening. The serrations or surface roughening may help to secure the holder to adjacent vertebrae during a spinal fusion procedure. A distractor or distractors of a holder may be tapered. The distraction provided by the holder may allow a separation distance between the vertebrae to be greater near anterior surfaces of the vertebrae. The tapered distractor or distractors may allow insertion of an implant or implants that provide lordotic adjustment.
A holder may be affixed to a pair of vertebrae during a spinal fusion procedure. In an embodiment of a holder, a tang is driven into a vertebra to affix the holder to the vertebrae. The tang may include serrations or surface roughening that securely couples the holder to the vertebra. In an embodiment a tang is driven into each vertebra of a pair of vertebrae. In alternate embodiments, holders may include fastener openings. Fasteners may be driven into a vertebra or into the vertebrae through the fastener openings to fasten the holder to the vertebrae. The fasteners may be, but are not limited to, screws, nails, rivets, trocars, pins, and barbs.
Protective sleeves may be inserted into, and may be removed from, conduits in a holder. A portion of the sleeve may have a window or slot located adjacent to the top of the holder. The window may serve as a view-port to provide increased visibility near the procedure site. A keyway in the sleeve may be placed over a pin in a body of the holder during insertion of the sleeve into the holder. When the pin engages the keyway, the sleeve may be rotated to secure the sleeve within holder. The pin and keyway may ensure that the window is positioned in a desired location. In embodiments of sleeves and dual sleeve holders, the desired location of the window is adjacent to a second conduit in the holder after the sleeve is inserted and rotated in a first conduit of the holder. The position of the window may inhibit tissue or blood vessels from being damaged by instruments inserted within the sleeve.
In some embodiments, the inner surfaces of the conduits may contain shoulders to limit the insertion distance of protective sleeves in the conduits. Above a shoulder, a conduit may be sized to match the outer diameter of a protective sleeve. Below the shoulder, the conduit may be sized to match the outer diameter of instrument heads and implants to be used in the procedure. In some embodiments, the shoulder may include slots configured to engage distractors on protective sleeves; thus allowing the holder to be used with single-tube protective sleeves having distractors.
The height of a holder, when inserted in a disc space between two vertebrae, may be substantially less than a length of a protective sleeve. During a spinal fusion procedure, a protective sleeve may be inserted into a sleeve conduit of the holder when needed and removed when not needed without affecting alignment of the holder relative to the vertebrae. Removal of a protective sleeve from the holder may decrease the likelihood of a protective sleeve being inadvertently used as a lever arm during the procedure. Removing a protective sleeve from the holder may increase visibility at the procedure site. Removing a protective sleeve may also allow for easy access to the disc space to irrigate or aspirate the surgical site.
An advantage of a holder is that the holder may be securely coupled to vertebrae by a fastener and/or tangs. Securely coupling the holder to the vertebrae may maintain alignment and position of the holder throughout an implant insertion procedure. The holder may have a low profile. The low profile may inhibit the holder from being unintentionally contacted and moved during an implant insertion procedure. Further advantages of a holder may include that the holder is sturdy, durable, light weight, safe, simple, efficient, and reliable; yet the holder may also be easy to manufacture and use.
Another advantage of a holder is that a body of the holder may include a pin that engages a keyway of a sleeve positioned within a sleeve conduit. The pin and keyway may allow a window in the sleeve to be positioned at a desired location relative to the holder. The position of the window may provide increased visibility during the spinal fusion procedure. The position of the window may inhibit tissue from entering the window and contacting a portion of an instrument within the sleeve. The window may be positioned at a desired position by rotating the sleeve. In an embodiment, rotating the sleeve approximately 45xc2x0 after insertion into the sleeve conduit positions the window in the desired location. Material may be removed from the disc space through the opening without requiring removal of the sleeve from the holder or removing the material through the entire length of the sleeve.